2.5 S-curve Forecasting
The typical form of the relationship between project duration and expenditures incurred is S-shaped , where budget expenditures are initially low and increase rapidly during the major project execution stage before starting to level off again as the project gets nearer to its completion. The S-curve figure represents the project budget baseline against which actual budget expenditures will be evaluated. They help project managers understand the correlation between project duration and budget expenditures and a good sense of where the highest levels of budget spending are likely to occur. Forecasting the S-curve can help project managers generate estimates of expenditures during the various stages of the project duration.
The S-curve (also called a Pearl Curve) is based on what is known as the logistic or auto catalytic growth function . The Web site below has a complete discussion on the theory and the steps involved in S-curve forecasting. You are strongly urged to go over this document and follow through on the worked-out example. You may use this file to work on assignments for this lesson. See your online course Syllabus or Road Map for details.
http://leeds-faculty.colorado.edu/Lawrence/Tools?SCurve/scurve.xls